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< html >< head >< title > boost::mpl::copy</ title >
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< h1 >< a href = "../Table_of_Contents.html" >< img src = "../mpl_logo.jpg" alt = "[Home]" border = 0 align = "right" ></ a > copy</ h1 >< h3 > Synopsis</ h3 >
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< p >
< pre >
template<
typename Sequence
, typename State
, typename BinaryOp
>
struct copy
{
typedef < em > unspecified</ em > type;
};
</ pre >
< p >
< h3 > Description</ h3 >
< p >
< code > copy</ code > is, in fact, just another name for < code >< a href = "../Reference/fold.html" > fold</ a ></ code > . It was introduced for symmetry with < code >< a href = "../Reference/copy_if.html" > copy_if</ a ></ code > [< a href = "#1" > 1</ a > ], and because it's a nice name for one of the typical < code > fold</ code > applications, that is, copying the content of one sequence into another - see the example below.
< p >
< h3 > Definition</ h3 >
< p >
< pre >
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#include "< a href = "../../../../../boost/mpl/copy.hpp" > boost/mpl/copy.hpp</ a > "
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</ pre >
< p >
< h3 > Parameters</ h3 >
< table border = "1" >
< tr >< th > Parameter </ th >< th > Requirement </ th >< th > Description </ th ></ tr >
< tr >< td >< code > Sequence</ code ></ td >< td > A model of < a href = "../Sequence.html" > Sequence</ a ></ td >< td > A sequence to iterate. </ td ></ tr >
< tr >< td >< code > State</ code ></ td >< td > A type</ td >< td > The initial state for the first < code > BinaryOp</ code > application. </ td ></ tr >
< tr >< td >< code > BinaryOp</ code ></ td >< td > A model of [Lambda Function]</ td >< td > The operation to be executed on forward traversal. </ td ></ tr >
</ table >
< p >
< h3 > Expression semantics</ h3 >
< p >
< table border = "1" >
< tr >< th > Expression </ th >< th > Expression type </ th >< th > Precondition </ th >< th > Semantics </ th >< th > Postcondition </ th ></ tr >
< tr >< td >< code > typedef copy< Sequence,T,Op> ::type s;</ code ></ td >< td > A type</ td >< td ></ td >< td > Equivalent to < code > typedef fold< Sequence,T,Op > ::type s;</ code > .</ td >< td ></ td ></ tr >
</ table >
< p >
< h3 > Complexity</ h3 >
< p >
Linear. Exactly < code >< a href = "../Reference/size.html" > size</ a > < Sequence> ::type::value</ code > applications of < code > BinaryOp</ code > .
< p >
< h3 > Example</ h3 >
< p >
< pre >
typedef < a href = "../Reference/vector_c.html" > vector_c</ a > < int,0,1,2,3,4,5,6,7,8,9> numbers;
typedef copy<
< a href = "../Reference/range_c.html" > range_c</ a > < int,10,20>
, numbers
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, < a href = "../Reference/push_back.html" > push_back</ a > < _,_>
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> ::type result;
< p >
BOOST_STATIC_ASSERT(< a href = "../Reference/size.html" > size</ a > < result> ::value == 20);
BOOST_STATIC_ASSERT((< a href = "../Reference/equal.html" > equal</ a > < result,< a href = "../Reference/range_c.html" > range_c</ a > < int,0,20> > ::type::value));
</ pre >
< p >
< h3 > Notes</ h3 >
< p >
[< a name = "1" > 1</ a > ] In case if you wonder why < code >< a href = "../Reference/copy_if.html" > copy_if</ a ></ code > , in its turn, wasn't just called < code > fold_if</ code > , - something that would allow to eliminate the family of < code > copy</ code > algorithms completely - these two have quite different semantics.< br >
< p >
< h3 > See also</ h3 >
< p >
< a href = "../Algorithms.html" > Algorithms</ a > , < code >< a href = "../Reference/copy_if.html" > copy_if</ a ></ code > , < code >< a href = "../Reference/copy_backward.html" > copy_backward</ a ></ code > , < code >< a href = "../Reference/copy_backward_if.html" > copy_backward_if</ a ></ code > , < code >< a href = "../Reference/fold.html" > fold</ a ></ code > , < code >< a href = "../Reference/fold_backward.html" > fold_backward</ a ></ code >
< p >< hr >
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< a href = "../Table_of_Contents.html" > Table of Contents</ a >< br > Last edited May 20, 2003 1:36 am</ body ></ html >
